Browsing by Subject "Groundwater flow--Texas--Gulf Region"
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Item Heat variations caused by groundwater flow in growth faults of the South Texas Gulf Coast Basin(1985) Bodner, Daniel Paul; Sharp, John Malcolm, Jr., 1944-Zones of above average subsurface temperatures have been noted in certain areas of the Gulf Coast basin. Their cause has often been credited to geopressure, which presumably traps heat because of higher porosity and consequently lower thermal conductivity. I determined the temperature distribution in a portion of South Texas by collecting and analyzing over 1600 bottom-hole temperature measurements. The analysis included correcting the temperatures with the Kehle correction scheme, constructing isothermal surfaces by both interpolating and extrapolating the data, and Kriging the result. Temperature profiles were plotted for twelve subregions of the study area. The greatest temperature anomalies are associated with the Tertiary Wilcox growth fault zone, and the simple presence of geopressure is insufficient to account for the temperature anomaly. Numerical modeling indicates that growth faults act as zones for concentrated vertical flow. The upwelling of deep basinal fluids advects heat and causes the high temperatures observed in the growth fault zone. The model, by Smith (1983), is two-dimensional, finite element, steady state, and couples heat and fluid transport. It indicates that the source of these fluids is deep, perhaps over 20,000 feet (6096 m) below the surface. The modeling results also suggest that an unidentified region of high thermal and hydraulic conductivity could exist coastward of the Wilcox faults at a depth of about 15,000-20,000 feet (4572-6096m).Item Temperature variations and their relation to groundwater flow, South Texas, Gulf Coast Basin(1988) Pfeiffer, Deborah Susan, 1961-; Sharp, John Malcolm, Jr., 1944-Isothermal surfaces and temperature gradients confirm the presence of anomalously high geothermal gradients along the Wilcox growth fault zone in South Texas. This anomaly has been attributed to the advection of heat via upwelling basinal fluids. However, there is also evidence that the same processes are occurring along the Vicksburg/Frio growth fault zones. Although a previous study showed a general increase in the temperature gradient to the southwest within South Texas, this study demonstrates that the trend is discontinuous. Shallow data suggest that advecting fluids are escaping from the compactional regime and perturbing the temperature field within the overlying meteoric regime. This study enlarges the data base of Bodner (1985) by including temperature data of less than 200°F within the original study area and the entire range of temperature data to the south. Isothermal surfaces produced at 50°F intervals from 100°F to 400°F indicate that beginning with the 150°F isotherm, a perturbation occurs at approximately 3500 feet to 4500 feet (1070 to 1370 m) along the Wilcox growth fault trend -- well above the top of the geopressured, compactional regime. This perturbation suggests that advecting fluids are escaping from the compactional regime to the meteoric regime above. In addition, the isothermal surfaces show that the perturbation along the Wilcox growth fault trend becomes more prominent with depth. However, the isothermal surfaces do not show a perturbation along the Vicksburg/Frio growth fault trends. Temperature gradients calculated within numerous subregions of the study area confirm the presence of temperature gradients as high as 3.4°F/100 ft (62.2°C/km) within the Wilcox growth fault zone. In addition, a contour map of temperature gradients within the compactional regime reveals the presence of higher temperature gradients (> 2.5°F/100 ft or 45.8°C/km) within the Vicksburg/Frio growth fault zones. This is the only thermal evidence that processes occurring in the Wilcox growth fault zone may also be occurring in the Vicksburg/Frio growth fault zones. Finally, a contour map of temperature gradients within the meteoric regime indicates that the highest gradients (> 2.0°F/100 ft or 36.6°C/km) occur roughly along the Wilcox growth fault zone. As with the 150°F isotherm, this suggests that advecting fluids are escaping from the compactional regime and perturbing the temperature field in the overlying meteoric regime.